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Re: [dmarc-ietf] indeterminisim of ARC-Seal b= value

"John R Levine" <johnl@taugh.com> Tue, 28 March 2017 02:21 UTC

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Date: Mon, 27 Mar 2017 21:21:11 -0500
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From: John R Levine <johnl@taugh.com>
To: Peter Goldstein <peter@valimail.com>
Cc: dmarc <dmarc@ietf.org>
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Subject: Re: [dmarc-ietf] indeterminisim of ARC-Seal b= value
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> I think tightening up some currently allowed ambiguity in the ARC
> specification is a much simpler and much better solution.  I'm not sure why
> there's such concern about canonicalizing the format and ordering of some
> tag/value pairs.

If you think that's all it would take to make signature headers perfectly 
identical, you will be deeeply disappointed.  (Take a look at FWS in the 
ABNF and all of the other generic ABNF for message headers.)

I think what we've been saying is that the SMTP mail ecosystem has never 
tried to make stuff bit-for-bit reproducible, and even if you could hammer 
on the spec to make super strict rules for one particular header, it's 
unlikely that the people who are adapting their DKIM code would pay 
attention.

R's,
John

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